Within the systems of slab formwork, those intended for formwork of large surfaces use fundamentally a series of vertical props, drop bolsters, longitudinal beams which are mounted on said drop bolsters and formwork panels which are mounted on the foresaid beams. The drop bolsters allow the stripping of such panels and beams before final setting of the concrete.
However, for shuttering more reduced spaces, especially when the perimeter walls have already been built up, or in those constructions in which the surface finish is not too demanding, simpler formwork systems are used constituted basically by vertical props, fixed support bolsters and the shuttering panels which are mounted directly on those bolsters, the difference being that when stripping with the fixed bolsters, all the elements are removed at the same time, namely, the panels, the bolsters and the props, for which reason it is necessary to wait for final setting of the concrete before stripping.
Nevertheless, the fixed support bolsters can be used likewise in large-scale formwork to finish off corners or special situations of the formwork in which it is not possible to use drop bolsters, using in these cases and in a combined manner said drop bolsters and fixed bolsters.
Specifically, in the European Patents No 0685022 of Peri and 0297357 of Hünnebeck-RöRo GmbH, as well as in the German Patent No 324580 of Josef Maier, formwork systems are disclosed in which different types of fixed bolster are used upon each of which rest four adjacent formwork panels, that is concurrent in a corner, each company using its own bolsters which adapt to the geometry, also special, of its formwork panels.